Role of reactive oxygen species (ROS) in MAPK-mediated chemotropism and infectious growth of the plant pathogenic fungus Fusarium oxysporum

趋化性是一种指向化学梯度的生长，控制着真菌的基本过程，如营养获取、有性或无性融合和宿主感染。趋化分子的性质，以及趋化受体和下游信号通路在很大程度上是未知的。科尔多巴大学的寄主小组开发了一种定量测量真菌植物病原菌尖孢镰刀菌菌丝定向生长的方法。对趋化机制的遗传剖析导致了丝裂原活化蛋白激酶(MAPK)Mpk1的鉴定，它是尖孢镰刀菌对寄主植物信号的趋化反应中的一个重要组成部分。此外，根分泌物中的主要化学诱导剂是植物分泌的过氧化物酶，这表明活性氧物种(ROS)在MAPK介导的趋化信号中起作用。在这里，我们建议1)通过检测尖孢霉菌NOx缺失突变体中MAPK的磷酸化状态和趋化反应，研究ROS产生酶NADPH氧化酶(NOx)在MAPK信号和趋化生长调节中的作用；2)利用半胱氨酸在磺酸状态下捕获和定点突变的方法，鉴定受过氧化物酶ROS依赖活性修饰的真菌靶蛋白。我们预计，这些结果将揭示指导真菌致病的基本过程中ROS和MAPK信号的新的分子链接和下游靶标。这一知识将对新的抗真菌药物的开发感兴趣。总体而言，该项目结合了申请者和东道主研究所在真菌中的ROS信号和趋化生长方面的经验。此外，它还允许申请者在一个国际公认的研究小组从事前沿研究课题的工作，为她在未来几年在德国进行创新研究提供最佳准备。

Chemotropism, the directed growth towards a chemical gradient, governs essential processes in fungi such as nutrient acquisition, sexual or asexual fusion and host infection. The nature of the chemoattractant molecules, as well as the chemotropic receptors and downstream signaling pathways are largely unknown. The host group at University of Córdoba has developed a method to quantitatively measure directed hyphal growth in the fungal plant pathogen Fusarium oxysporum. Genetic dissection of the chemotropic mechanism led to the identification of a mitogen-activated protein kinase (MAPK), Mpk1, as an essential component in the chemotropic response of F. oxysporum to host plant signals. Moreover, the major chemoattractant in root exudates was identified as a plant-secreted peroxidase, suggesting a role of reactive oxygen species (ROS) in MAPK-mediated chemotropic signaling. Here we propose to 1) study the role of the ROS-generating enzymes NADPH oxidases (Nox) in regulation of MAPK signaling and chemotropic growth, by determining MAPK phosphorylation status and chemotropic response in F. oxysporum nox deletion mutants and 2) to identify fungal target proteins that are modified by the ROS-dependent activity of the peroxidase, using cysteine trapping in sulfenic acid state and site-directed mutagenesis. We anticipate that the results will uncover novel molecular links and downstream targets of ROS and MAPK signaling in fundamental processes guiding fungal pathogenicity. This knowledge will be of interest for the development of new anti-fungal drugs. Overall, this project combines the experiences of the applicant and the host institute regarding ROS signaling in fungi and chemotropic growth, respectively. Further, it allows the applicant to work on a cutting-edge research topic in an internationally recognized research group providing her with optimal preparation to undertake innovative research in Germany in the upcoming years.